Bug 1460920 - Part 2 : Support referrerpolicy attribute in script HTMLScriptElement r=hsivonen

The patch adds the support of referrerpolicy attribute in script element
and take the attribute into account when loading script.

Differential Revision: https://phabricator.services.mozilla.com/D11637

dom/html/HTMLScriptElement.cpp

@@ -259,6 +259,12 @@ HTMLScriptElement::GetCORSMode() const
   return AttrValueToCORSMode(GetParsedAttr(nsGkAtoms::crossorigin));
 }
 
+mozilla::net::ReferrerPolicy
+HTMLScriptElement::GetReferrerPolicy()
+{
+  return GetReferrerPolicyAsEnum();
+}
+
 bool
 HTMLScriptElement::HasScriptContent()
 {